This invention relates to a light-emitting device and a method for manufacturing the same, and more particularly to a light-emitting device with lens function and a method for manufacturing the same.
Examples of light-emitting element used for optical communication are a semiconductor laser and a LED. In order to optically couple such light-emitting element highly efficiently and easily to an optical fiber which is an optical transmission medium, rapid developments are being made on a light-emitting element module of the type in which a light-emitting element and a lens are combined and a light-emitting device of the type in which a light-emitting element itself is given with lens function. These conventional light-emitting devices will be described by referring to FIGS. 6 to 8.
FIG. 6 is a schematic sectional view showing a state of optical coupling between a light-emitting element, a lens and an optical fiber which are disposed separately, FIG. 7 is a schematic sectional view showing a state of optical coupling between a light-emitting device having an integral lens and an optical fiber, and FIG. 8 is a schematic sectional view showing a state of optical coupling between a light-emitting device a portion of which is lens-shaped and an optical fiber. In FIGS. 6 to 8, the reference numeral 18 denotes a light-emitting element, 19 a light-emitting surface, 20 a lens, 21 an optical fiber, 22 a lens united with the light-emitting element, 23 an adhesive, and 24 a lens formed in a portion of the light-emitting device. As shown in FIG. 6, when disposing the light-emitting device 18 and the lens 20 as separate parts, the optical axes of the lens 20 and the optical fiber 21 are each required to be aligned with that of the light-emitting element 18 so that the efficiency of optical coupling between the light-emitting element 18 and the optical fiber 21 is increased, and therefore the optical axis alignment is troublesome and takes a considerable length of time. To cope with this, the lens 22 is placed just above the light-emitting surface 19 and fixed to the light-emitting element 18 with the adhesive 23 so that the lens 22 is united with the light-emitting element 18 as shown in FIG. 7, and a portion of the light-emitting element 18 located just above the light-emitting surface 19 is lens-shaped so as to give the lens function to the light-emitting device as shown in FIG. 8, in which cases the optical axis alignment can be simplified because the separate operation for aligning the optical axis of the lens can be dispensed with and the number of parts required for the coupling between the light-emitting device and the optical fiber can be decreased.
However, in the conventional light-emitting device with lens function described above, when fixing the lens to the light-emitting element with an adhesive and the like, there are involed problems that the process of gluing the lens to the light-emitting element is needed and that the glued portion between the light-emitting element and the lens lacks in long-term stability and reliability. Meanwhile, in the light-emitting device a portion of which is lens-shaped as well, since the process of shaping into the lens form, e.g., ion etching, is still in the technologically developing stage, there is involved a problem that it is difficult to shape into the desired form and hence the efficiency of optical coupling to the optical fiber is low and the productivity of the light-emitting device is low.
The present invention aims to solve the above problems of the prior arts and an object of the invention is to provide a highly reliable light-emitting device which is constructed such that a lens made of radiation sensitive resin is formed directly on a light-emitting element so as to be located just above a light-emitting surface and which is capable of allowing the optical axes of the light-emitting element and optical fiber to be aligned more easily and making optical coupling between them with high efficiency, and a light-emitting device manufacturing method capable of manufacturing a highly reliable light-emitting device with high productivity, which device is capable of allowing the optical axes of the light-emitting element and optical fiber to be aligned more easily and making optical coupling between them with high efficiency.